1. Field of the Invention
This invention relates to a distillate fuel composition containing a thiadiazole and a tolyltriazole adduct as copper and silver corrosion inhibitors, and its use to reduce copper and silver corrosion in fuel delivery systems and internal combustion engines.
2. Description of the Related Art
It is well known that elemental sulfur, hydrogen sulfide and other sulfur compounds, contained in hydrocarbon streams are corrosive and damaging to metal equipment, particularly copper and copper alloys. Sulfur and sulfur compounds may be present in varying concentrations in the refined fuel and additional contamination may take place as a consequence of transporting the refined fuel through pipelines containing sulfur contaminants. Sulfur has a particularly corrosive effect on equipment such as brass valves, gauges and in-tank fuel pump copper commutators.
A commonly used technique for inhibiting corrosion of copper, steel or copper alloys in fuel systems is by the use of corrosion inhibitors. These additives are either sulfur scavengers or metal deactivators that coat metal surfaces preventing sulfur components to react with the metal. Many such corrosion inhibitors are known. For example, U.S. Pat. No. 3,663,561 discloses 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazoles which are stated to be useful as sulfur scavengers and U.S. Pat. No. 5,035,720 relates to a corrosion inhibiting composition comprising an oil-soluble adduct of a triazole and a basic nitrogen compound.
It would be desirable to have a copper and silver corrosion inhibitor which would protect copper and silver at low treat rates when exposed to a variety of fuels under different conditions, which would not produce high levels of insolubles or cause injector sticking in diesel engines, and which would inhibit silver corrosion in two-cycle engines.